MEMS device

Abstract

A MEMS transducer, for instance a MEMS capacitive transducer, comprising: a flexible membrane, the flexible membrane comprising a conductive track; and a continuity testing circuit electrically connected to the conductive track. The conductive track may be electrically isolated from any further conductive regions of the flexible membrane. The continuity testing circuit is configured to test the continuity of the conductive track.

The invention claimed is: 
     
       1. A MEMS transducer comprising:
 a flexible membrane, the flexible membrane comprising a conductive track; and 
 a continuity testing circuit electrically connected to the conductive track, wherein the conductive track is electrically isolated from any further conductive regions of the flexible membrane, and 
 
       wherein the continuity testing circuit is configured to test the continuity of the conductive track; 
       wherein:
 the MEMS transducer further comprises a substrate; 
 the flexible membrane is attached to the substrate; 
 the conductive track is located within a perimeter region of the flexible membrane, a mechanical attachment between the flexible membrane and the substrate being located in the perimeter region of the flexible membrane; 
 the flexible membrane is attached to the substrate at a plurality of supporting edges located in the perimeter region of the flexible membrane, the conductive track being located at each of the supporting edges; and 
 the plurality of supporting edges alternate around the perimeter of the flexible membrane with a plurality of unfixed edges, the conductive track being located at each of the unfixed edges. 
 
     
     
       2. The MEMS transducer of  claim 1 , wherein the conductive track is electrically connected to the continuity testing circuit at two discrete positions. 
     
     
       3. The MEMS transducer of  claim 2 , wherein the conductive track is divided into a plurality of conductive track portions, each conductive track portion being electrically connected to the continuity testing circuit. 
     
     
       4. The MEMS transducer of  claim 3 , wherein each of the conductive track portions is electrically isolated from the other conductive track portions from among the plurality of conductive track portions. 
     
     
       5. The MEMS transducer of  claim 1 , wherein:
 the perimeter region of the flexible membrane is supported on a plurality of mount structures, the plurality of mount structures being configured to restrict the movement of the flexible membrane with respect to the substrate; and 
 the conductive track is configured to substantially encircle a mount structure from among the plurality of mount structures. 
 
     
     
       6. The MEMS transducer of  claim 1 , wherein:
 the perimeter region of the flexible membrane comprises a plurality of spring portions separated by perforations in the flexible membrane; and 
 the conductive track is configured to follow a serpentine path along and around the spring portions. 
 
     
     
       7. The MEMS transducer of  claim 1 , wherein the continuity testing circuit is a current sensing circuit or wherein the continuity testing circuit is a voltage sensing circuit. 
     
     
       8. The MEMS transducer of  claim 1 , wherein the conductive track is formed substantially from metal. 
     
     
       9. The MEMS transducer of  claim 1  wherein:
 the flexible membrane comprises a dispersed layer located on a surface of the flexible membrane, a portion of the dispersed layer being configured to act as a membrane electrode in a capacitive system; and 
 the conductive track is formed from a further portion of the dispersed layer that is electrically isolated from the portion of the dispersed layer configured to act as the membrane electrode in the capacitive system. 
 
     
     
       10. The MEMS transducer of  claim 1 , wherein:
 the MEMS transducer comprises a back plate portion, the back plate portion comprising a back plate electrode; and 
 the conductive track is electrically isolated from the back plate electrode. 
 
     
     
       11. The MEMS transducer of  claim 1 , wherein the continuity testing circuit is configured to perform a continuity test of the conductive track upon activation of the MEMS transducer. 
     
     
       12. The MEMS transducer of  claim 1 , wherein the continuity testing circuit is configured to perform continuity tests of the conductive track periodically while the MEMS transducer is active. 
     
     
       13. The MEMS transducer of  claim 1 , wherein the continuity testing circuit is configured to continuously test the continuity of the conductive track while the MEMS transducer is active. 
     
     
       14. A MEMS transducer comprising a flexible membrane, the flexible membrane comprising a conductive track,
 wherein the conductive track is electrically isolated from any further conductive regions of the flexible membrane, and 
 wherein the conductive track is electrically connected to a plurality of bond pads, the bond pads being for connection to a continuity testing circuit; and 
 wherein: 
 the MEMS transducer further comprises a substrate; 
 the flexible membrane is attached to the substrate; 
 the conductive track is located within a perimeter region of the flexible membrane, a mechanical attachment between the flexible membrane and the substrate being located in the perimeter region of the flexible membrane; 
 the flexible membrane is attached to the substrate at a plurality of supporting edges located in the perimeter region of the flexible membrane, the conductive track being located at each of the supporting edges; and 
 the plurality of supporting edges alternate around the perimeter of the flexible membrane with a plurality of unfixed edges, the conductive track being located at each of the unfixed edges. 
 
     
     
       15. A method for testing the status of a flexible membrane of a MEMS transducer, the flexible membrane comprising a conductive track, the MEMS transducer further comprising a continuity testing circuit electrically connected to the conductive track, wherein the conductive track is electrically isolated from any further conductive regions of the flexible membrane, and wherein the continuity testing circuit is configured to test the continuity of the conductive track, wherein: the MEMS transducer further comprises a substrate; the flexible membrane is attached to the substrate; the conductive track is located within a perimeter region of the flexible membrane, a mechanical attachment between the flexible membrane and the substrate being located in the perimeter region of the flexible membrane; the flexible membrane is attached to the substrate at a plurality of supporting edges located in the perimeter region of the flexible membrane, the conductive track being located at each of the supporting edges; and the plurality of supporting edges alternate around the perimeter of the flexible membrane with a plurality of unfixed edges, the conductive track being located at each of the unfixed edges, the method comprising:
 sending an electrical current along the conductive track using the continuity testing circuit; and 
 evaluating the properties of the electrical current using the continuity testing circuit to test the continuity of the conductive track, 
 wherein the continuity of the conductive track indicates the status of the flexible membrane.